Aircraft aerodynamic empennages with divided control surfaces (inboard and outboard) for Horizontal tail plane (HTP) elevator or Vertical tail plane (VTP) rudder are very well known in the prior art. Weight and cost saving is one of the most important issues in aircrafts design so there is a continuous optimization need.
Elevators are control surfaces placed on both sides of the Horizontal Tail Plane (HTP) of an aircraft, and they are used to control the pitch of the aircraft. Similarly to the case of the torsion box, elevators are mainly multi-rib structures made of composite materials, formed by at least a main spar, and a plurality of ribs supporting upper and lower panels.
Elevators are usually constructed as one assembly. Although in very large commercial aircraft, they are split in two different sub-assemblies, inboard and outboard elevators. Similarly, in the case of rudders for large aircraft, the same concept is applied to the rudder design, with upper and lower rudders.
Another known structure for control surfaces, especially for flaps or low size control surfaces such as ailerons, is the composite multi-spar architecture, which can be an option over traditional multi-rib structures, with the aim of both weight and cost reduction. A multi-spar structure is formed only by spars and cover panels, so that the ribs are replaced by a number of spars longitudinally arranged.
FIG. 2 shows a prior art typical architecture for large aircraft aerodynamic surface (1) comprising a torsion box (2) having a front spar (21) and rear spar (22), a first control surface (3) comprising a front spar (31) and a trailing edge (32) and a second control surface (4) comprising a front spar (41) and a trailing edge (42), and hinge fittings (6,8) and actuators fittings (5, 7) as means for pivotally attaching the first control surface (3) and the second control surface (4) to the rear spar (22) of the torsion box (2). The first control surface (3) shown in FIG. 2 is the outboard elevator which comprises fifteen ribs (33) and one spar (31) and the second control surface (4) is the inboard elevator which comprises nine ribs (43) an one spar (41).
Different rib configuration for control surfaces are known. However in the case of aircraft aerodynamic surfaces comprising inboard and outboard control surfaces (typically found in large aircrafts), best compromise between manufacturing simplification and weight reduction is to be found.